A window regulator for an automotive vehicle has a plurality of guide rails in a space located between inner and outer door panels of a door, which guide rails are disposed in parallel with one another so as to provide substantially vertical up and down movement of a window glass, so that the window glass moves in and out of the door. The guide rails, respectively, slidably mount thereon sliders which interconnect by an X-link or a cable the window glass and either a power operated device or a manually operated device. A driving force from the power or manual operating device acts on the window glass at a point where the slider secures the window glass.
To avoid the window glass of a sashless door from inclining inwardly or outwardly with respect to the sashless door during upward movement of the window glass, it has been proposed to extend the guide rails to a triangular corner of a door window opening of the door. Such a window regulator is known from Japanese Unexamined Patent Publication No. 61(1986)-250279.
A drawback to the use of such window regulators for, in particular, sashless doors is that the window glass, in addition to inward or outward inclination, is often subjected to tilting back and forth when the window glass is moved up or down, which has the effect of impeding a smooth opening and closing motion of the window. This is because there is a design requirement according to an automotive body appearance that the window glass of an automotive door window has a slight inward inclination toward a vehicle compartment. When guide rails for guiding up and down movement of the window glass are vertically inclined, a moving path or trajectory is unavoidably complicated to move the window glass diagonally and, due to the complexity of the moving path, the window glass is imbalanced and the center of gravity of the window glass moving up or down changes in position, resulting in a stiff motion called a slip and stick motion.